Fluorescent lamp starter including a glow switch contiguous and thermally connectred o a thermal switch



Dec. 15, 1964 L. w. COOK ETAL 3,161,746

FLUORESCENT LAMP STARTER INCLUDING A GLOW SWITCH CONTIGUOUS AND THERMALLY CONNECTED TO A THERMAL SWITCH Filed Jan. 21, 1963 ERT I. SCHAUSDL BY W @MMW/i ATTORNEY United States Patent 3,161,745 FLUQRESCENT LAMP STARTER TNCLUDENG A GLOW SWETCH CGNTHGUGJUS ANT) THERMAL- LY CONNECTED T8 A THERMAL SWTTQH Leonard W. Cook and Robert I. Schauseil, Warwick, RL, assignors to General Electric Company, a corporation of New York Filed Jan. 21, 1963, Ser. No. 2552,665 11 tlllaims. (Cl. Nil-4.13.5)

This invention relates to a starting apparatus for electron discharge devices and, in particular, to apparatus for initiating the discharge in a fluorescent lamp.

Fluorescent lamps and other gaseous discharge devices require a high starting voltage but, once started, can operate on a much lower voltage. Normally, fluorescent lamps are designed for operation on conventional residential voltages but these voltages are insufficient to start the lamps. The starting voltage is provided by including an induction element, i.e. a ballast, and a glow switch starter in the fluorescent lamp circuit. Conventionally, the glow switch comprises a gas-filled tube within which a bimetal contact strip is slightly spaced from a fixed contact strip, the two metals forming the bimetal strip being disposed so that when heat is applied to the bimetal strip, it will close the gap between the contact strips.

The circuit arrangement with the fluorescent lamp is such that, when the lamp-operating switch is closed, a glow discharge occurs between the two contact strips of the glow switch and this discharge heats the bimetal strip, causing it to be deflected into contact with the fixed contact strip. A relatively large current then flows from the power source through the glow switch contacts, the induction element, and through the lamp filaments, heating them in preparation for the final act of starting. In addition, the glow discharge between the two contact strips of the switch ceases and the binietal strip begins to cool, breaking contact with the fixed contact strip. In response to this interruption of the current flow in the circuit, the induction element produces a high voltage transient surge which strikes an are between the heated filaments of the fluorescent lamp. Conduction thereafter takes place within the lamp and the glow switch remains out of operation.

However, if the voltage surge fails to start the fluorescent lamp, the glow discharge is again established between the contact strips of the glow switch and the cycle is repeated. This causes undesirable blinking or flickering of the lamp. Prior art fluorescent lamp starters have attempted to eliminate this blinking by sensing the continued unsuccessful efforts of the glow switch to start the lamp. To this end, prior art starters have employed a heat source, which is responsive to the current which flows through the lamp circuit to preheat the lamp filaments while the glow switch contacts are closed, and a thermal switch, responsive to the heat generated by the heat source, to disable the glow switch. The present invention obviates the use of a separate heat source to actuate the no-blink'mechanism and renders the operation of the no-blink mechanism dependent only on the voltage characteristics of the glow switch and independent of line voltage or circuit current variations as normally encountered.

It is an object of the invention to provide an improved fluorescent lamp starter.

It is another object of the invention to provide an improved starter for fiuorescent lamps incorporating an automatic reset no-blink mechanism.

It is another object of the invention to provide an auto- 3,161,746 Patented Dec. 15, 1964 matic reset, no-blink starter for fluorescent lamps which utilizes fewer components prior art starters.

It is another object of the invention to provide an explosion-proof, automatic reset, no-blink starter.

It is a further object of the invention to provide a fluorescent lamp starter which utilizes the heat developed by the glow switch to actuate the no-blink mechanism.

It is a further object of the invention to provide a fluorescent lamp starter with an improved thermal arrangement to promote increased reliability of the noblink mechanism.

Briefly stated, in accordance with one embodiment of the invention, a glow switch having normally open contacts and a thermal switch having normally closed contacts are serially connected across the terminals of the starter. Each switch has a hermetically sealed metal housing which forms one of the contacts, the housings being welded together to effect the serial connection of the switches. The welded joint serves to thermally as well as electrically interconnect the glow and thermal switches. The heat generated by the glow discharge of the glow switch, in attempting unsuccessfully to start the fluorescent lamp, causes the contacts of the thermal switch to open, thereby disabling the glow switch and terminating the blinking of the fluorescent lamp. The thermal switch thus functions as the automatic reset, noblink mechanism. A resistance heater, connected across the terminals of the starter, generates suflicient heat upon opening of the thermal switch contacts to maintain these contacts open. Another embodiment of the invention utilizes a metal strap surrounding the resistance heater, the metal strap being thermally connected to the glow and thermal switches to preheat the resistance heater and to improve the transmission of heat from the resistance heater to the thermal switch after opening of the thermal switch contacts.

The subject matter of the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation may best be understood by reference to the following description taken in connection with the accompanying drawing, in which:

FIGURE 1 is an exploded isometric view of one embodiment of the automatic reset, no-blink, fluorescent lamp starter of the invention;

FIGURE 2 is a cross-sectional side view of the glow and thermal switches of the fluorescent lamp starter illustrated in FIGURE 1;

FIGURE 3 is a circuit diagram schematically illustrating the fluorescent lamp starter of the invention and its interconnection with a power source, a ballast, and a fluorescent lamp; and

FIGURE 4 is an exploded isometric View of another embodiment of the automatic reset, no-blink fluorescent lamp starter of the invention.

With reference to FIGURE 1, the fluorescent lamp starter of the invention employs a conventional starter base 1, formed of insulating material, with a cylindrical metal casing 2, having an insulating liner 3, cooperating with base It to form an enclosure for the starter. A pair of protruding terminals 6 are mounted in base 1 by means of swaging or staking, as indicated by reference numeral 7. The enlarged ends 8 of terminals 6 cooperate with a conventional starter socket to electrically connect the starter in a fluorescent lamp circuit. The portions i of terminals 6 are hollow, thereby facilitating connection of the electrical leads of the starter components thereto, since the leads may be inserted in the hollow portions and securely fastened therein by a drop of solder.

A glow switch llli is mounted on base l by the insertion of metal rod M, which is an electrical lead of the glow switch, in the hollow portion 9 of one of the terminals while a thermal switch 12 is similarly mounted by the connection of metal rod 13 to the other terminal.

FIGURE 2, which is a cross-sectional side view of glow switch and thermal switch 12, illustrates in greater detail the structure of the switches. Glow switch ill is of the type described and claimed in the copending application of Leonard W. Cook, Serial Number 61,467, filed October 10, 1960, now Patent Number 3,098,137, and assigned to the assignee of the present invention. Switch 10 comprises a metal housing 14 in the form of a hollow cylinder closed at one end to form a generally flat interior end surface 15 perpendicular to the cylinder axis, the open end of the hollow cylinder having a flange 16 formed thereon. Metal housing 14 serves as a contact of the switch. The open end of the metal housing 14 is closed by an assembly comprising metal eyelet or ring 17, glass ring 18 positioned in the metal ring 17, and metal terminal rod 11 positioned in the glass ring 18. Metal rod 11 serves as an electrical lead of the glow switch, as illustrated in FIGURE 1. The assembly is attached to metal housing 14 to form a hermetically-sealed enclosure by means of a bond between flange 16 and ring 17, rod 11 being insulated from housing 14 by glass ring 18. A bimetal strip 20 is mounted on rod 11 and positioned centrally in housing 14-, the free end of the strip being slightly spaced from end surface 15. A contact 21 is provided on the free end of the strip 20. Glow switch 10 thus has normally open contacts. The interior of the housing is filled with an ionizable gas to provide a glow discharge between strip 24 and surface 15 upon application of an appropriate potential between rod 11 and housing 14, bimetal strip 26 deflecting due to the heat of the glow discharge so that contact 21 touches the wall of housing 14 to complete an electrical circuit through the switch.

Thermal switch 12 is structurally similar to glow switch 10 with the exception that the bimetal strip 22 is initially mounted so that contact 23 at its free end touches the wall of metal housing 24 and is arranged to deflect, upon heating, away from the wall 24 to open the electrical circuit. Thermal switch 12 thus has normally closed contacts, metal housing 24 serving as a contact. In addition, the hermetically sealed housing is filled with a nonionizable, arc-suppressing, non-oxidizing gas. The gas in thermal switch 12 is at a pressure above atmospheric to improve its arc-quenching characteristics. The hermeti Cally-sealed enclosures of the thermal switch contacts and the glow switch contacts render the starter of the invention explosion-proof and tamper-proof. In both the glow and the thermal switches, the bimetal strips are easily adjusted during manufacture to control the temperatures at which the contacts will open or close.

As illustrated in FIGURES 1 and 2, metal housing M of glow switch Jill and metal housing 24 of thermal switch 12 are electrically and thermally connected by means of a welded bond 25 between the adjacent portions of flanges 16 overlying metal rings 17. Glow switch 1%), having normally open contacts, and thermal switch 12, having normally closed contacts, are thus serially connected between terminals 6.

A resistance heater 26 is connected between lead 111 of thermal switch ll) and lead 13 of thermal switch 12 and is thus connected across terminals 6. Resistance heater 26 is energized upon opening of the normally closed contacts of thermal switch 12 and the heat generated thereby maintains the contacts of switch 12 open. A capacitor 27 is connected across terminals 45 in parallel with the serial combination of glow switch in and thermal switch 12 in order to provide radio interference suppression.

FIGURE 3 illustrates the connection of the starter of FIGURE 1 in a circuit with an AC source 28, a lampoperating switch 29, a ballast 3n, and a fluorescent lamp 7 31. Upon closure of lamp-operating switch 29, the potential of AC source 28 is applied through the series circuit comprising ballast 3t and filaments 32 and 33 of fluorescent lamp 31 to terminals 6 of the starter. Contacts Z3 and 24 of thermal switch 12 being closed, approximately the full voltage of the source is applied across bimetal element 20 and metal housing 14 of glow switch It) to initiate a glow discharge therebetween. The glow discharge heats up the bimetal strip 20 causing it to defiect and close contacts 21 and 14. Closure of these contacts applies the voltage of the AC source 28 to lamp filaments 32 and 33 heating them to electron emission temperature. Closure of the contacts also shorts out the glow discharge, permitting bimetal strip 26 to cool, the bimetal strip returning, after a short period of time, to its normally undefiected position and opening contacts 21 and 14. In response to the resulting interruption of current flow in the circuit, ballast 30 produces a transient voltage surge in an effort to maintain the current flow, this surge normally establishing an arc discharge between filaments 32 and 33 of lamp 31 to light the lamp.

In the event that the lamp is defective and does not light, the starting cycle of the glow switch it) is repeated, the glow switch generating heat during each cycle due to the glow discharge. The continued unsuccessful eliorts of glow switch it) to start the defective lamp raises the temperature of metal housing M, the temperature reaching approximately 215 F. The weld 2S permits etlicient heat transfer from metal housing 14 of glow switch 10 to metal housing 24 of thermal switch 12. After a predetermined period, for example, one to two minutes, the temperature of bimetal strip 22 of thermal switch 12 is increased to a point where it dei'lects, separating contacts 23 and 24.

Thermal switch 12, actuated by the heat generated by glow switch It? and functioning as the no-blink mechanism, thus elfectively disconnects glow switch in from the circuit and precludes further attempts to start the defective lamp. At the same time that the glow switch 10 is disabled by thermal switch 12, resistance heater 26 is energized and begins to generate heat in response to current flow from source 28 therethrough. As long as lampoperating switch 29 is closed, resistance heater 26 gen crates enough heat to maintain the bimetal strip 22 of thermal switch 12 deflected and switch contacts 23 and 24 open. Upon the opening of lamp-operating switch 2?, the generation of heat in resistance heater 26 ceases and bimetal strip 22 returns to its normal undeliected position, closing contacts 23 and 24 to automatically reset the no blink mechanism for subsequent operation.

FIGURE 4 illustrates another embodiment of the automatic reset, no-blink, fluorescent lamp starter of the invention wherein improved thermal characteristics and reliability are attained. The arrangement is identical with that of the FIGURE 1 embodiment with the exception that a metal strap .34 is wrapped around the insulated body of resistance heater 26 with the projecting ends 35 of the strap sandwiched and welded between abutting flanges lid of glow switch it! and thermal switch 12.

Strap 34 functions to preheat resistance heater 26 during 7 the cycling of glow switch 1% due to the thermal contact of projecting ends 35 with metal housing 14 of glow switch ltl. Upon opening of the normally closed contacts of thermal switch 12, in response to heat generated by the repeated cycling of glow switch it}, the metal strip 34 also more eifectively transfers the heat generated in the resistance heater 26 to thermal switch 12 due to the thermal contact of projecting portions 35 with metal housing 24. Because of this improved thermal arrangement, in particular the preheating of resistance heater 26,

the probability of the thermal switch contacts closing shortly after opening because of initial insuficient heat generation by resistance heater 26 is minimized, thereby increasing the reliability of the no-blink mechanism. The

advantages of preheating the resistance heater and im:

proving the heat transfer from the resistance heater to the thermal switch may be individually attained, if desired, by arranging the metal strap 34 to contact either glow switch or thermal switch 12. The use of metal strap 34 surrounding resistive heater 26 also increases the life of the resistance heater since heat is more etticiently dissipated therefrom.

Although the invention has been described with reference to specific embodiments, the invention is not limited to these embodiments. Many modifications within the spirit and scope of the invention will be obvious to those skilled in the art. It is thus intended that the invention is not limited to the particular details shown and described which may be varied without departing from the spirit and scope of the invention and the appended claims.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A fluorescent lamp starter comprising:

(a) a pair of terminals,

(b) a glow switch having normally open contacts,

(0) a thermal switch having normally closed contacts,

(d) means connecting said glow switch and said thermal switch in electrical series circuit across said pair of terminals,

(e) said glow switch and said thermal switch being contiguous and thermally connected so that heat generated by said glow switch due to repeated cycling thereof causes said normally closed contacts of said thermal switch to open, and

(f) a resistance heater connected across said pair of terminals, said heater being energized upon opening of the normally closed contacts of said thermal switch to maintain said normally closed contacts open.

2. A fluorescent lamp starter comprising:

(a) a pair of terminals,

(b) a glow switch comprising:

(1) a hermetically-sealed metal housing,

(2) a terminal rod extending through one end of said housing and connected to one of said pair of terminals, said terminal rod being insulated from said housing, and

(3) an elongated bimetal strip mounted on said rod in the interior of said housing, said bimetal strip being deformable into contact with said housing when subjected to a predetermined temperature,

(c) a thermal switch comprising:

(1) a hermetically-sealed metal housing,

(2) a terminal rod extending through one end of said housing and connected to the other of said pair of terminals, said terminal rod being insulated from said housing, and

(3) an elongated bimetal strip mounted on said rod in the interior of said housing so as to contact said housing and being deformable to break contact with said housing when subjected to a predetermined temperature,

(d) means electrically and thermally connecting said glow switch and said thermal switch housings so that heat generated by said glow switch due to repeated cycling thereof causes said normally closed contacts of said thermal switch to open, and

(e) a resistance heater connected across said pair of terminals, said heater being energized upon opening of the normally closed contacts of said thermal switch to maintain said normally closed contacts open.

3. The fluorescent lamp starter of claim 2 in which an arc suppressing gas is contained in said metal housing of said thermal switch.

4. The fluorescent lamp starter of claim 2 in which a metal strap thermally connects said resistance heater and said housing of said glow switch.

5. The fluorescent lamp starter of claim 2 in which a metal strap thermally connects said resistance heater and said housing of said thermal switch. 1

6. The fluorescent lamp starter of claim 2 in which a metal strap surrounding said resistance heater thermally connects said resistance heater to said housings of said glow and said thermal switches.

7. The fluorescent lamp starter of claim 2 which includes a metal strap surrounding said heater and in which said means electrically and thermally connecting said housings of said glow and thermal switches comprises portions of said metal strap sandwiched between said housings.

8. A fluorescent lamp starter comprising:

(a) a pair of terminals,

(1)) a glow switch having normally open contacts,

(0) a thermal switch having normally closed contacts,

(d) means connecting said glow switch and said thermal switch in electrical series circuit across said pair of terminals,

(e) said glow switch and said thermal switch being contiguous and thermally connected so that heat generated by said glow switch due to repeated cycling thereof causes said normally closed contacts of said thermal switch to open,

(f) a resistance heater connected across said pair of terminals, said heater being energized upon opening of the normally closed contacts of said thermal switch to maintain said normally closed contacts open, and

(g) means thermally connecting said resistance heater to said glow and said thermal switches.

9. The fluorescent lamp starter of claim 8 in which said last-named means comprises a metal strap surrounding said resistance heater and in contact with said glow and said thermal switches.

10. A fluorescent lamp starter comprising:

(a) a pair of terminals,

(b) a glow switch having normally open contacts,

(0) a thermal switch having normally closed contacts,

(d) means connecting said glow switch and said thermal switch in electrical series circuit across said pair of terminals,

(c) said glow switch and said thermal switch being contiguous and thermally connected so that heat generated by said glow switch due to repeated cycling thereof causes said normally closed contacts of said thermal switch to open,

(1) a resistance heater connected across said pair of terminals, said heater being energized upon opening of the normally closed contacts of said thermal switch to maintain said normally closed contacts open, and

(g) a metal strap thermally connecting said resistance heater and said glow switch.

11. A fluorescent lamp starter comprising:

(a) a pair of terminals,

(11) a glow switch having normally open contacts,

(0) a thermal switch having normally closed contacts,

(d) means connecting said glow switch and said thermal switch in electrical series circuit across said pair of terminals,

(e) said glow switch and said thermal switch being contiguous and thermally connected so that heat generated by said glow switch due to repeated cycling thereof causes said normally closed contacts of said thermal switch to open,

(f) a resistance heater connected across said pair of terminals, said heater being energized upon opening of the normally closed contacts of said thermal switch to maintain said normally closed contacts open, and

(g) a metal strap thermally connecting said resistance heater and said thermal switch.

References Cited in the file of this patent UNITED STATESv PATENTS Perkins et al. a Mar. 22,1960 

1. A FLUORESCENT LAMP STARTER COMPRISING: (A) A PAIR OF TERMINALS, (B) A GLOW SWITCH HAVING NORMALLY OPEN CONTACTS, (C) A THERMAL SWITCH HAVING NORMALLY CLOSED CONTACTS, (D) MEANS CONNECTING SAID GLOW SWITCH AND SAID THERMAL SWITCH IN ELECTRICAL SERIES CIRCUIT ACROSS SAID PAIR OF TERMINALS, (E) SAID GLOW SWITCH AND SAID THERMAL SWITCH BEING CONTIGUOUS AND THERMALLY CONNECTED SO THAT HEAT GENERATED BY SAID GLOW SWITCH DUE TO REPEATED CYCLING THEREOF CAUSES SAID NORMALLY CLOSED CONTACTS OF SAID THERMAL SWITCH TO OPEN, AND (F) A RESISTANCE HEATER CONNECTED ACROSS SAID PAIR OF TERMINALS, SAID HEATER BEING ENERGIZED UPON OPENING OF THE NORMALLY CLOSED CONTACTS OF SAID THERMAL SWITCH TO MAINTAIN SAID NORMALLY CLOSED CONTACTS OPEN. 